A large number of ostomy bags for receiving bodily waste from colostomy or ileostomy patients have been proposed in the prior art.
European patent application No. 0 607 028 discloses an ostomy bag for holding body waste comprising an envelope formed of flexible plastic sheet material defining a waste collection chamber. The envelope defines a gas outlet proximate a top end portion of the envelope and spaced from a waste inlet opening of the envelope. A deodorizing filter is joined to the envelope in alignment with the gas outlet means for deodorizing gaseous waste material before the gaseous waste exits from the bag through the gas outlet. In the envelope, there is provided means for protecting the deodorizing filter from contact by semi-liquid waste material, and for permitting the flow of gaseous waste, and for obstructing the flow of semi-liquid waste, the protection means comprising a porous protection film preceding the deodorizing filter. The protection means further comprises open cell foam material preceding the porous protection film such that the gaseous waste must pass through the open cell foam material, and through the porous protection film before it passes through the filter. It is thereby sought to provide a multi-stage filter system that prevents semi-liquid waste material from contaminating a deodorizing element but does not inhibit evacuation of gaseous waste through the deodorizing filter.
U.S. Pat. No. 6,135,976 discloses an ostomy appliance comprising a front wall and a rear wall of flexible material, the rear wall having an opening into the bag by which waste material can enter the bag. One of the walls has one or more vents through which gas may escape from the bag. The appliance has a filter covering the vent, the filter comprising an elongated, substantially flat filter body of a porous filter material interposed between gas and liquid impervious walls which are sealed to the body along its longitudinal side edges. Gas inlet and outlet opening are provided in communication with the filter material adjacent to its respective longitudinal end regions. The gas and liquid impervious walls are sealed to the upper end lower surfaces of the filter body. In use, gas flows longitudinally through the filter from the inlet opening to the outlet opening. The inlet opening is covered with a microporous hydrophobic and oleophobic membrane, and the foam material is placed between the front wall and the rear wall and covers the inlet opening of the vent. The appliance of U.S. Pat. No. 6,135,986 thereby shows improved resistance against wetting and blocking of the filter.
It has been found that porous filter arrangements as those suggested in the prior art may tend to clog due to faeces being deposited therein, whereby the drainage bags, including the filters, may have to be replaced at relatively short intervals. It is therefore and object of preferred embodiments of the present invention to provide an ostomy system with a filter arrangement which does not clog as rapidly as the prior art filter arrangements.